Adie's syndrome is a neurological condition characterized by a dilated pupil in one eye, which reacts slowly to light. This condition occurs due to damage to the nerves that control the pupil's response. People with Adie's syndrome may also experience difficulty focusing on nearby objects, a condition known as accommodation. The exact cause of Adie's syndrome is often unknown, but it can be associated with viral infections or autoimmune responses. It is generally considered a benign condition, meaning it does not lead to serious health issues. Treatment is usually not necessary, but some individuals may benefit from glasses for near vision.